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The electrocatalytic reduction of CO 2 (CO 2 RR) into value-added hydrocarbons is limited due to high limiting potential (U L) and competing hydrogen evolution reaction (HER). To find the best catalyst for CO 2 reduction the concept of hydrogen poisoning was not considered in the catalyst screening process. Herein, we present a simple screening method and graphical construction using multiparameter optimization for the design of highly active and selective single-atom catalysts (SAC) using density functional theory calculations. A series of SAC namely, MN4, MBN3 and H@MBN3 (M: metal) are investigated for CO 2 RR. Our results revealed that MN4 and MBN3 SAC are not favorable for CO 2 RR due to high U L > −0.85 V and hydrogen poisoning (ΔG H* < 0), respectively. H@MBN3 SAC (stable compounds forming H–B bonds) are identified as efficient catalysts with a low value of U L and significantly hinder the competitive HER. Among these, H@CoBN3 and H@FeBN3 SAC show excellent CO 2 RR activity with limiting potential −0.30 and −0.44 V respectively for CH 4 production and no chance of HER. Scaling relations reveal the importance of *COOH/*CHO binding energy (E b) as an energy descriptor to evaluate the catalytic performance. This work provides a new theoretical perspective to design a highly selective catalyst for CO 2 RR. [Display omitted] • Simple graphical construction is provided to screen the catalyst for selective CO 2 RR. • The hydrogen poisoning issue is addressed, which blocks the active site. • Hydrogen assisted catalysts (H@MBN3) are designed for highly efficient CO 2 RR. • The binding energy of *COOH is defined as an energy descriptor for SAC catalyst. [ABSTRACT FROM AUTHOR]

A facile gas-steamed strategy is reported for preparing heteroatom dual-doped hierarchical porous hollow carbon catalysts via carbonization of a mixture of carbon sphere precursor and ammonium fluoride (NH 4 F). Notably, NH 4 F can be decomposed into NH 3 and HF by pyrolysis, in which HF gas can etch SiO 2 pellets to form hollow structure while the N and F atoms can be introduced at the same time. The FCS-900 exhibits admirable electrocatalytic properties with the highest onset potential and limiting current density in neutral electrolytes (0.944 V vs. RHE and 6.44 mA cm−2). In comparison to MFC-Pt, much higher output voltage and power density (0.617 V and 1093.6 ± 6.26 mW m−2) are obtained by MFC-900. Such results can be attributed to the largest specific surface area of FCS-900 to supply exposed active sites and fast transportation channels. Based on X-ray photoelectron spectroscopy, the FCS-900 catalyst possesses the active substances of pyridinic/graphitic N and C-F bonds. The synergism of N and F can effectively facilitate the adsorption of O 2 during ORR, as further supported by density functional theory calculation. The facile and green synthesis strategy can be extended to design metal-free carbon-based electrocatalysts with superior electrocatalytic performance. [Display omitted] • A gas-steamed strategy is proposed to prepare N-F co-doped hollow carbon spheres. • NH 4 F is endowed with dual functions of etching SiO 2 and N-F co-doping. • The FCS-900 has highly active substances of pyridinic/graphitic N, C-F bonds. • The MFC-900 shows the highest power density of 1093.6 ± 6.26 mW m−2. [ABSTRACT FROM AUTHOR]

Herein, atomically dispersed Ni–N 3 –C materials are facilely synthesized by the pyrolysis of Ni-doped ZIF-8. Each single Ni atom is proved to be bonded with three N atoms to form Ni–N 3 sites by X-ray absorption spectroscopy. During the pyrolysis at high temperature, the increasing of relative contents and blue-shift binding energy of pyrrolic N can be observed, indicating the Ni might be bonded with pyrrolic N. Moreover, the formation energy (E f) of NiN 3 -pyrrolic structure is smaller than that of NiN 3 -pyridinic calculated by density functional theory (DFT), thus confirming the dominated bonding structure of NiN 3 -pyrrolic further. The optimum material can achieve an ultra-high CO Faradaic efficiency of 99.37% at −0.75 V vs. RHE with a turnover frequency (TOF) of 3498 h−1 and a high CO partial current density of 80 mA cm−2 at −1.15 V vs. RHE, which is among the best Ni catalysts. Based on DFT results, the NiN 3 -pyrrolic sites can facilitate both the formation of COOH* intermediate and desorption of CO, which can also suppress the competitive hydrogen evolution reaction (HER) simultaneously, thus resulting in high catalytic activity and selectivity from CO 2 to CO. Electroreduction from CO 2 to CO with high activity and selectivity are achieved on the single-atom Ni–N–C catalyst due to the dominated Ni coordination structure by three pyrrolic N atoms. [Display omitted] • Single Ni atom catalysts were synthesized with Ni-doped ZIF-8 as precursor. • NiN 3 -pyrrolic coordination structure was identified as the dominated active sites. • Ultra-high activity and selectivity for CO 2 reduction towards CO was achieved. • NiN 3 -pyrrolic sites can promote the formation of *COOH intermediate by DFT. [ABSTRACT FROM AUTHOR]

Efforts to fabricate high-conducting and high-strength free-standing graphene/carbon nanotube (CNT) buckypaper through room-temperature functionalization have been frustrated by the defective surface of the graphene and CNTs. In this study, high-quality graphene sheets were prepared via an amino-assisted liquid phase exfoliation method and used to integrate with CNTs to form free-standing flexible graphene/CNTs buckypaper. After that, individual graphene and CNT of the graphene/CNTs buckypaper were linked via diazonium chemistry to generate covalent bonds. By tuning functionalization time, the functionalized graphene/CNTs buckypaper exhibits an electrical conductivity of 87,500 S/m and a Young's modulus of 22.3 GPa, which are 6 and 10 times higher, respectively, than unfunctionalized graphene/CNTs buckypaper. Density functional theory calculations demonstrate that charge transfer rate (K et) of the aryl linker bonded moiety configuration via covalent functionalization is an order faster than without the aryl linker bonded moiety configuration. Unprecedently, the capacitance of the functionalized graphene/CNTs buckypaper is 359.6 mF/cm3 at a scan rate of 1 mV/s with no capacitance change after 10,000 cycles of testing. This work sheds the light of the value of molecular engineering in the design of novel composite for flexible electronics, energy storage and provides important insights into the understanding of basic principles of covalent functionalization of graphene/CNTs. The functionalized graphene/CNTs buckypaper were crosslinked to form covalent bonds between individual material via diazonium chemistry reaction and it achieved an electrical conductivity of 875 S/cm and Young's modulus of 22.3 GPa, which are 6 and 10 times higher than unfunctionalized graphene/CNTs buckypaper. Besides, charge transfer rate (K et) of the functionalized graphene/CNTs shows ten times faster than unfunctionalized moiety configuration. [Display omitted] [ABSTRACT FROM AUTHOR]

SiC-supported graphene intercalated by a two-dimensional Pb monolayer can provide an appealing platform for spintronic applications. Such a monolayer structure is thermodynamically ultrastable, as observed in recent experiments. However, important fundamentals such as the structure of intercalated phases, locations of intercalated atoms, thermodynamic preference for intercalation, and intercalation pathways for this system have not yet been understood conclusively. In this work, extensive density functional theory calculations are performed to assess Pb intercalation thermodynamics and kinetics under graphene on SiC(0001). We find that intercalation of isolated Pb atoms is strongly disfavored over adsorption on top of graphene. However, intercalation of complete Pb layers in the gallery between SiC and graphene buffer layer is strongly favored over supported Pb monolayers and moderately favored over formation of supported large three-dimensional Pb islands. We also find that initiation of intercalation either by individual Pb atoms directly penetrating graphene or by hopping under a static graphene step edge is energetically prohibitive at experimental temperatures. Consequently, more complex intercalation pathways are operative and further analyzed. We demonstrated that once an intercalated Pb monolayer forms around a graphene step edge, a facile Pb mass transport by Pb vacancy-mediated diffusion can be triggered for continued growth of the intercalated monolayer. [Display omitted] [ABSTRACT FROM AUTHOR]

Defect-enriched carbon nanomaterials possess high potassium storage capacity and rapid ion transport capability; nevertheless, their rate performance is restricted by the deteriorated electronic conductivity induced by over-broken sp2-C conjugated structure. Herein, intrinsic defect-enriched carbon nanosheet (DCS) with controllable defect density is reported for the high-efficiency anode of potassium-ion batteries (PIBs). The DCS constructed by internal sp2-C configuration and external sp3-C defects can ensure good electron transport ability and afford abundant active sites for K+ storage. As PIBs anode, DCS-24 obtained by ball-milling for 24 h with optimized defect density delivers a high specific capacity of 270.9 mAh g−1 at 0.5 C, an excellent rate performance (189 mAh g−1 at 10 C), as well as long cycle durability (255.1 mAh g−1 over 3000 cycles at 1 C). Electrochemical results and density functional theory simulations indicate that the intrinsic defects of carbon materials improve the capacitive K+ storage capacity, speed up the K+ diffusion, and lower the K+ adsorption energy. [Display omitted] • DCS with controllable defect density is prepared by ball-milling. • Enhanced performance is achieved by the regulation of defect density. • DCS-24 delivers a high capacity of 255.1 mAh g−1 over 3000 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Metal-free catalysts for hydrogenation reactions using molecular hydrogen (H 2) are a major challenge in the field of catalysis. The Frustrated Lewis Pairs (FLPs) systems and heteroatom-doped carbon materials as metal-free catalysts are currently the mainstream research in hydrogenation reactions. Here, a series of oxygen-induced zigzag graphene (OZG) was constructed over thermal treatment of reduced graphene oxide (rGO) and applied as metal-free catalysts in nitrobenzene hydrogenation. The OZG-800 (thermal treatment at 800 °C) shows promising performance activity with 99.7% nitrobenzene conversion and 94.4% selectivity to aniline. The experimental results indicate that the zigzag edge and medium-strong acid sites formed by oxygen species may be the active centers in nitrobenzene hydrogenation. The density functional theory (DFT) calculations are in accord with experimental results that the zigzag edge and oxygen species play a critical role in H 2 activation and dissociation. This work provides a promising route for the rational design of metal-free catalysts for hydrogenation. Oxygen-induced zigzag graphene was constructed over thermal treatment of reduced graphene oxide and applied as metal-free catalysts in nitrobenzene hydrogenation. The catalyst shows promising performance activity with 99.7% nitrobenzene conversion and 94.4% selectivity to aniline. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphene nanoflakes (GNFs), with intriguing zigzag edge magnetism, have great potential for the application in high-speed and low-power nanoelectronics and spintronics. However, scattering from edge defects can substantially degrade this novel edge magnetism. Precisely controlled growth of GNFs with zigzag edges on dielectric substrates to suppress edge defect scattering is still challenging. Herein, we report the successful synthesis of triangular zigzag-edged GNFs via epitaxy on hexagonal boron nitride (h -BN) templates. Further magnetic measurement results indicate the triangular zigzag-edged GNFs embedded in h -BN can induce the magnetization with a magnitude of 1e-4 emu/g at room temperature. Additionally, density functional theory calculations address such magnetic orderings originating from the superexchange interactions among local "unpaired" electrons located in the zigzag C−BN interface. Our in-plane hetero-integration approach to the template-epitaxial growth of GNFs on the pre-etched h -BN provides a promising platform for experimentally achieving GNFs with high electron spin states, which are highly desired for next-generation spintronics and nanoelectronics. [Display omitted] [ABSTRACT FROM AUTHOR]

Contrary to the monotype intercell connection in a hexagonal structure material, newly synthesized stable monolayer C 60 fullerene (mC 60) lattice possesses two kinds of intercell connection, and anisotropic properties are thus expected. Herein, we have investigated the anisotropy mechanical properties of the mC 60 using first-principles calculations within the framework of density functional theory (DFT) and theoretical analysis. Uniaxial tensile properties of mC 60 are orientation-dependent, and the ultimate tensile strength and the work-to-fracture of mC 60 reach their maxima at 15° and minima at 75°, respectively. A theoretical expression, based on strain-governed bond failure criterion, has been developed for the strength-loading direction relationship of mC 60. The theory captures well with the orientation-dependent strength from DFT calculations. We further illustrate that mC 60 's band gap may be largely tuned through strain engineering. Our atomistic insights and the theoretical on the structure – mechanical property relationship might be helpful in the exploring of the functioning and application of mC 60 , which may be further generalized to the mechanical analysis of other monolayer lattices. [Display omitted] [ABSTRACT FROM AUTHOR]

Building van der Waals heterostructures (vdWHs) is an effective method to broaden two-dimensional (2D) material applications in multifunctional devices. However, few broken-gap vdWHs are realized, which limit 2D materials development in the tunnel field-effect transistors. Here, based on the density functional theory, we theoretically design the stable 2D C 3 N/MX(M = Ga, In; X = S, Se, Te) vdWHs, where the band-to-band tunneling (BTBT) exists due to the broken-gap band alignment. The negative electric field expands the tunneling window, while multifunctional band alignment can be realized under positive electric field. Moreover, the I–V curves present the obvious negative differential resistance behavior. This work provides the understanding of physical mechanism and possible applications for 2D broken-gap vdWHs. C 3 N/MX (M = Ga, In; X = S, Se, Te) vdWHs possess broken-gap band alignment, obvious negative differential resistance behavior and multifunctional band alignment under electric field. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent years, a number of three-dimensional (3D) porous metallic carbon allotropes have been proposed to be used as anode materials for metal-ion batteries by assembling graphene or penta-graphene nanoribbons. Here, based on density functional theory and tight-binding model, we design a new 3D porous metallic carbon monolith (termed Hex-C 568) consisting of PHP-graphene nanoribbons which contain pentagonal, hexagonal and octagonal rings. It is thermally, dynamically and mechanically stable. We find that its metallicity is attributed to the delocalized electrons in the p -orbitals of the sp 2 hybridized carbon atoms, and Hex-C 568 is a promising anode material for Na-ion batteries with high performance. Its reversible gravimetric and volumetric capacities are 787.53 mAhg−1 and 718.10 mAhcm−3, respectively, with low diffusion energy barrier (0.04–0.30 eV), low average open-circuit voltage (0.26 V), and small volume change during the charging/discharging process (3.71%). These electrochemical properties are superior to those of most recently reported anode materials, suggesting that PHP-graphene nanoribbon is a promising building unit for the design of novel carbon anode materials going beyond graphene and penta-graphene. [Display omitted] • Going beyond graphene and penta-graphene nanoribbons, we design a new stable 3D porous metallic carbon allotrope Hex-C 568 by using PHP-graphene nanoribbons as the building block. • Hex-C 568 has rich binding sites and regularly distributed channels for the adsorption and transport of Na ions, showing promise as an anode material for SIBs. [ABSTRACT FROM AUTHOR]

Using carbon black and formamide as raw materials, a N-doped carbon black electrocatalyst (NC) with good performance was prepared by a simple method for the electrochemical CO 2 reduction reaction (ECRR). At −0.86 V vs. RHE, the prepared NC800 catalyst achieves 97.8% of CO selectivity and 9.1 mA cm−2 of CO partial current density, which is higher than most carbon-based electrocatalysts reported so far. In order to better explore the role of nitrogen and oxygen functional groups in carbon-based materials, the nitrogen and oxygen contents in the NC800 catalyst were changed by nitric acid oxidation and thermal desorption. The results show that nitrogen content can effectively improve the CO selectivity of nitrogen-doped carbon materials, but excessive oxygen content inhibits the ECRR activity. It was found for the first time that the ratio of N/(N + O) in carbon catalysts was positively correlated with CO Faraday efficiency and its partial current density, indicating that carbon materials with high nitrogen doping amount and low oxygen content would benefit the ECRR performance, which was also supported by density functional theory calculation. These new understandings provide new insights into the preparation of highly efficient carbon-based catalysts for ECRR. [Display omitted] • N doped carbon black electrocatalyst (NC) is prepared using a simple method. • NC achieves 97.8% CO selectivity for electrochemical CO 2 reduction reaction (ECRR). • The excessive oxygen content in NC will inhibit the ECRR activity. • The ratio of N/(N + O) in carbon is positively correlated with CO faraday efficiency. • High N doping amount and low O content are beneficial to improve ECRR performance. [ABSTRACT FROM AUTHOR]

Silver-doped diamond-like carbon (Ag-DLC) films are considered as promising materials for the surface modification of mechanical components and biological implants. The long-term stability of Ag-DLC films is essential for their commercial use and requires intensive investigation. In this study, DLC and 10.0 at.% Ag-DLC films were prepared using a hybrid deposition technique, and the existence and evolution of Ag atoms over time were systematically studied. The results show that Ag atoms with a lower Ehrlich–Schwoebel barrier than that of C atoms are more prone to interlaminar diffusion, refining the columnar structure of DLC films and thereby creating a compact structure. In the as-deposited Ag-DLC film, Ag atoms mainly existed as fine nanocrystals with sizes ranging from 3 to 5 nm. Ag elements diffused with time during its long-time service, and fine Ag nanocrystals agglomerated to form large nanocrystals. The calculation results by density functional theory confirmed that the proximity of Ag atoms can lower the system energy, rendering agglomeration thermodynamically stable. Molecular dynamics simulations verified the spontaneous migration and agglomeration behaviors of Ag atoms over time. This study was focused on the evolution of Ag-DLC films over time and would provide guidance for their use in long-term applications. [Display omitted] • Ag atoms are more prone to interlaminar diffusion than C atoms. • Ag nanocrystals in Ag-DLC film agglomerate during its long-time service. • Proximity of Ag atoms in Ag-DLC film is thermodynamically stable. • Ag atoms in Ag-DLC film spontaneously agglomerate over time. [ABSTRACT FROM AUTHOR]

Carbon based electrocatalysts are well known promising candidates for the oxygen reduction reaction (ORR), but the random approach to find the best catalyst using experimental method delayed the screening process and it leads to a huge cost with less proficiency. Using Quantum Mechanics followed by Machine Learning (QM/ML) approach, we can predict the best catalyst faster way and the origin of the cause can be identified for further development of carbon-based catalyst. Using the π electronic descriptor unveiled using density functional theory, we applied the analytical simple fit method and six different machine learning algorithms to develop a highly effective predictive model to estimate ΔG OH. Furthermore, structural relations of ZGNR and AGNR are demonstrated to estimate the D π (E F), R-O π , and ΔG OH of different widths of ribbon that reduces additional DFT calculations. By applying both SVR predictive model and structural relations, we predicted the ORR performance of 2500 sites of GNRs and listed a few most ideal active carbon sites with lower overpotential (η < 0.5V). To validate our study, we predicted the ORR performance of different sites in 0D, 1D, 2D doped graphene systems using SVR model and confirmed the values with the DFT computed results. [Display omitted] • We proposed a QM/ML based predictive model to estimate site-specific ORR activity. • π orbital descriptors are used as features in machine learning methods. • SVR predictive model is developed to find accurate ORR activity of graphene system. • Structural correlation between descriptors and width of nanoribbon is identified. [ABSTRACT FROM AUTHOR]

N-doped rGO (N-rGO) based nano materials are considered to be competent candidates for absorbing electromagnetic waves (EMWs), owing to the low filler loading and abundant relaxation polarization losses. With a unique multistage porous structure, NiFe@N–C/rGO, derived from the composite of NiFe-MOF anchoring on GO nanosheeets, was successfully constructed by a facile solvothermal method and high-temperature annealing technique. Adjusting the ratio of GO is an effective strategy to optimize the EMWs absorption performance to a large extent. At a filler loading of 20 wt%, when the content of graphene is 30 mg, the corresponding product NiFe@N–C/rGO-30 is found to have a minimum reflection loss (RL min) of −72.28 dB at 10.82 GHz, and an effective absorption bandwidth (EAB, RL ≤ −10 dB) is 5.25 GHz (12.43–17.68 GHz) under the matching thickness of 2.46 mm, its EAB dramatically reached 7.14 GHz (9.74–16.88 GHz) when the graphene content was increased to 90 mg at 2.04 mm matching thickness, which covers most of the X and Ku radar frequency band. Combined with the analysis of the electronic and surface structures of NiFe@N–C/rGO composites, the formation energy and dipole moment were calculated to reveal the mechanism of EMWs absorption within them. The results show that the N-doped structure is more stable than the vacancy modification, where the pyridinic-N is the source of dipole relaxation polarization under high-frequency electromagnetic field. The combination of experimental and theoretical research reveals the inherent mechanism of EMWs attenuation in as-prepared composites, paving an inspirational route for controllable high performance absorbing materials. [Display omitted] • The composites consist of hollow spherical NiFe-MOF derivative and N-rGO were first constructed. • The center frequency of the EAB in the different bands are tunable by adjusting the ratio of rGO. • NiFe@N–C/rGO-90 exhibits the EAB of 7.14 GHz with a thickness 2.04 mm and a low filler loading 20 wt%. • The formation energy and the dipole moment of N-rGO are calculated based on density functional theory. [ABSTRACT FROM AUTHOR]

2D MXenes (transition metal carbides, Ti 3 C 2 T x) with large surface area and metallic conductivity are widely used as supporters in catalysts. Unfortunately, the single MXene sheets would deteriorate in the presence of oxygen and water, which is almost the same as the environment of oxygen reduction reaction (ORR). Herein, an "armor" was constructed to encapsulate the oxidizable MXene by a confined in-situ oxidative polymerization strategy, employing the electrostatic interaction between the exfoliated MXene sheets (negatively charged) and oxidant (Fe3+, positively charged). The ultra-dispersed binary Fe 3 N and Co sits coupled with the large surface area MXene supporter synergy to endow more exposed active sites, meanwhile, the density functional theory (DFT) studies reveal that a moderate binding strength between the intermediates and the binary active sites was effectively modulated to enhance the ORR performance. The synthesized Fe 3 N/Co–N–C@MXene exhibits an impressive half-wave potential (E 1/2 , 0.871V) and a lower Tafel slope of 52.56 mV dec−1 than that of Pt–C-20% (74.89 mV dec−1). The Fe 3 N/Co–N–C@MXene based ZAB exhibits a four times higher peak power density (189.16 mW cm−2) than the Pt–C-20% based ZABs and superior cycle stability within 320 h. Furthermore, the assembled flexible ZABs shows high flexibility and stability in different bending scenarios. [Display omitted] • Ultra dispersion binary Fe 3 N/Co–N–C encapsulated MXene composites for ORR. • Large surface area and uniformly distributed active sites synergize for a high-performance ORR catalyst. • About four times higher peak power density (189.16 mW cm−2) than that of Pt–C-20%. • High-stability zinc-air battery with a voltage gap merely increased by 36 mV in 320 h. • High flexible zinc-air battery for different bending scenarios. [ABSTRACT FROM AUTHOR]

In the last decade, surface-assisted reactions involving well-defined molecular precursors have led to the controlled assembly of several clean-edged and defect-free graphene nanoribbons. The recent realization of a bisanthene-like quantum dot with pairs of pentagon–heptagon, or Stone–Wales (SW), defects has been successfully achieved. Based on the similarity between the pristine and SW-defective bisanthene blocks, we propose a set of systems based on the concatenation of SW-bisanthene motifs and study their electronic properties using density functional theory. We demonstrate that nanoribbons with SW-defects preserve the semiconducting character of their pristine counterparts. Furthermore, noteworthy behaviors involving the frontier levels emerge, which affect carrier mobilities of both electrons and holes. We also investigate the electronic transport properties of nanojunctions composed by graphene nanoribbons with a localized distribution of SW-defects compatible with the geometry of the corresponding bisanthene-like blocks. Our simulations shown that the transmission spectrum is sensitive to the position and concentration of SW-defects. [Display omitted] [ABSTRACT FROM AUTHOR]

Li-ion capacitors (LICs) have emerged as a novel energy-storage device to bridge the performance gap between Li ion batteries and supercapacitors. Herein, by employing waste tire pyrolysis oil (WTPO) as carbon precursor, N-doped graphene nanolayer (N-GNL) is directly prepared by a one-step template-induction methodology without any subsequent purification processes, according to the self-decompositon behavior of g-C 3 N 4. Benefiting from the unique layered structure and N doping, the N-GNL affords satisfactory anode behavior with respect to capacity and rate performance. Moreover, the positive contributions of improving electronic conductivity and Li storage ability for N doping are revealed by density functional theory calculation. Besides, a full LIC fabricated with N-GNL anode and asphalt-derived cubic porous carbon cathode not only displays significantly better electrochemical performance than LIC configured with commercial activated carbon cathode and graphite anode, but also delivers outstanding Ragone performance and exceptional durability. This work also provides a feasible route to realize high efficient conversion of petroleum asphalt and WTPO into high-performance electrode materials. [Display omitted] • The N-GNL is prepared by a one-step template-induction methodology using WTPO as carbon source. • The N-GNL presents satisfactory anode performance with respect to capacity and rate performance. • The N-GNL//CPC LIC delivers outstanding Ragone performance and exceptional durability. [ABSTRACT FROM AUTHOR]

Graphene-like nanomembranes made of the neighboring elements of boron, carbon and nitrogen elements, are well-known of showing outstanding physical properties. Herein, with the aid of density functional theory (DFT) calculations, various atomic configurations of the graphene-like BCN nanosheets are investigated. DFT results reveal that depending on the atomic arrangement, the BCN monolayers may display semimetallic Dirac cone or semiconducting electronic nature. BCN nanosheets are also found to exhibit high piezoelectricity and carrier mobilities with considerable in-plane anisotropy, depending on the atomic arrangement. For the predicted most stable BCN monolayer, thermal and mechanical properties are explored using machine learning interatomic potentials. The room temperature tensile strength and lattice thermal conductivity of the most stable BCN monolayer are estimated to be orientation-dependent and remarkably high, over 78 GPa and 290 W/m.K, respectively. In addition, the thermal expansion coefficient of the monolayer BCN at room temperature is estimated to be −3.2 × 10−6 K−1, which is close to that of the graphene. The piezoelectric response of the herein proposed BCN lattice is also predicted to be close to that of the h-BN monolayer. Presented results highlight outstanding physics of the BCN nanosheets. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond nanothread (DNT), which has been recently found to outperform other conventional carbon-based nanomaterials, is a promising reinforcer for polymer composites. Here, we find that DNT can significantly improve the frictional resistance of polymethyl methacrylate (PMMA) composites via atomistic simulations and density functional theory (DFT) calculations. Results show that the friction coefficient of PMMA composite is reduced by 25.98% with the incorporation of DNT due to the excellent interfacial interactions including vdW interaction and mechanical interlocking. These lead to reduced cohesive energy at the Fe-PMMA interface and lower polymer mobility. The improvement of frictional resistance is more significant by nitrogen-doped DNT (by 43.72%) due to the rougher landscape of molecular electronic potential and larger binding energy, resulting in better interfacial interactions. Besides, it is found that the improvement of frictional resistance by DNT is less significant at elevated temperatures. The degrading mechanisms are attributed to the generation of free volume at the DNT-PMMA interface, which decreases the interfacial shear strength and weakens the interfacial interactions. These findings could make advances towards the understanding of physical mechanisms governing the frictional properties of polymer composites, and provides useful guidance for the design of advanced polymer composites with good service life. [Display omitted] [ABSTRACT FROM AUTHOR]

Efficient, stable, and selective photocatalytic conversion of nitric oxide (NO) into nitrogen dioxide (NO 2) is highly desirable but remains a big challenge. We prepare single atom catalyst (SAC) by anchoring single Pd atoms onto graphitic carbon nitride (CNPd) via chemical impregnation followed by calcination. The prepared CNPd SAC is confirmed by aberration-correction high-angle-annular-dark field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. The synthesized SAC outperforms its competitors reported earlier for photocatalytic removal of NO under visible light and simulated sunlight irradiation in terms of selectivity and stability. The SAC maintains a NO removal efficiency of 83% and an instantaneous selectivity for NO 2 of 92.8% over 117.6 h under simulated sunlight with the inlet NO concentration of 12 ppm. This duration is about 23.5 times the longest duration tested for other catalysts in the literature. The experimental results and density functional theory (DFT) calculations reveal that single Pd atom promotes the photocatalytic degradation of NO. Moreover, the DFT calculations prove that the nitrate ions that accumulate on the surface of the SAC can react with NO to produce NO 2. This reaction enhances the selectivity for NO 2 and stability of the SAC. The CNPd catalyst exhibits high photocatalytic activity, selectivity and stability for the removal of NO under visible light. [Display omitted] • The CNPd SACs exhibit stable and high photocatalytic removal of NO. • The CNPd SACs show ultra-high selectivity for the conversion of NO into NO 2 which can be easily addressed by wet scrubbing. • NO removal efficiency of CNPd SACs remain 83% after solar irradiation over 117.6 h. • DFT calculations reveal the mechanism of photocatalytic over CNPd SACs. • DFT calculations explain the reason for selective conversion of NO to NO 2. [ABSTRACT FROM AUTHOR]

Graphite or graphene due to its excellent tribological properties is highly expected in solid lubrications, where the friction behaviors are intimately related to interfacial adhesion; however, the fundamental mechanism governing their correlation remains scientifically intriguing and largely unexplored. Through the combination of atomic force microscopy (AFM) measurements and density functional theory (DFT) calculations, we demonstrated that the friction of graphite surface slid against various AFM probes is generally enlarged with stronger adhesive interaction due to the higher interfacial charge density. The correlation between friction and adhesion mainly originates from the sliding induced charge evolution which governs the energy dissipation of solid lubrication between graphite and bulk materials. A general strategy that suppresses charge flowed into contact region enables the superlubricity of graphene or graphite surface owing to the feeble adhesion of the sliding systems. It is thereby proposed that the superlubricity is generally favored by weak interaction of the sliding interfaces. [Display omitted] • Nonlinear dependence of friction on adhesion is shown in tests and simulations. • Superlubricity of graphite against a Al 2 O 3 AFM tip is demonstrated. • Friction of HOPG is enlarged by adhesion due to higher interfacial charge density. • Graphene modification for an active SiO 2 tip enables superlubricity on HOPG surface. [ABSTRACT FROM AUTHOR]

The controllable growth of multilayer graphene is a challenging research topic. Prior results show graphene adlayers can grow beneath pre-existing graphene layers on a Cu(111). The conventional inverted-wedding-cake (IWC) model used to describe this incurs an energy disadvantage due to deformation in the overlying graphene. We propose an alternative theoretical model, the sunk growth mode, for understanding multilayer graphene growth on Cu substrates. Extensive density functional theory (DFT) calculations show that multilayer graphene grown via this sunk mode is energetically favourable compared to the on-terrace growth mode for Cu(111). These results reveal that graphene underlayers tend to grow in a sunk growth mode, minimizing deformation in the overlayers, reducing deformation energy. Further density functional tight binding-molecular dynamic (DFTB-MD) simulations on Cu(111) substrates yield sunken structures consistent with our sunk growth mode. Moreover, AFM investigations of experimentally grown multilayer graphene on polycrystaline Cu show that while friction data indicates multiple graphene edges in the sample, the topological height measurement indicates flat graphitic sheets, further confirming our sunk growth mode. This discovery provides a novel and more reasonable model for the "underlayer" growth of multilayer graphene and can be extended to a general theory for the multilayer graphene growth on various substrates. [Display omitted] [ABSTRACT FROM AUTHOR]

The weak hydrogen adsorption and slow catalytic kinetics are unfavorable for MoS 2 as a catalyst for hydrogen evolution reaction (HER) in alkaline solution. Herein, carbon quantum dots (CQDs) with high proton adsorption energy were expected to enhance the proton adsorption of MoS 2 during the HER process. The CQDs activated MoS 2 can establish a suitable hydrogen adsorption gradient due to the surface charge redistribution to promote the hydrogen spillover pathway. After the CQDs were loaded on MoS 2 , the charge distribution would gradually transfer from the C sites of CQDs to the S sites on MoS 2 surface, showing a charge gradient distribution calculated by density functional theory predictions. The adsorbed hydrogen can spill over from hydrogen-enriched CQDs to hydrogen-deficient MoS 2 in HER. The process could be monitored by the quasi in-situ electrochemical impedance spectroscopy. The enhanced hydrogen spillover effect by CQDs activated MoS 2 can pave the way for the design and preparation of efficient and low-cost catalysts. [Display omitted] • The hydrogen spillover effect was induced by the introduction of proton-collection CQDs. • The induced hydrogen spillover pathway can be attributed to the gradient charge distribution. • Surface charge redistribution was estimated by differential charge density and XPS analysis. • Hydrogen spillover pathway was described by DFT calculations and quasi in-situ EIS techniques. [ABSTRACT FROM AUTHOR]

Diamond displays outstanding chemical, physical, and tribological properties, making it attractive for numerous applications ranging from biomedicine to tribology. However, the reaction of the materials with molecules present in the air, such as oxygen, hydrogen, and water, could significantly change the electronic and tribological properties of the films. In this study, we performed several density functional theory calculations to construct a database for the adsorption energies and dissociation barriers of these molecules on the most relevant diamond surfaces, including C(111), C(001), and C(110). The adsorption configurations, reaction paths, activation energies, and their influence on the structure of diamond surfaces are discussed. The results indicate that there is a strong correlation between adsorption energy and surface energy. Moreover, we found that the dissociation processes of oxygen molecules on these diamond surfaces can significantly alter the surface morphology and may affect the tribological properties of diamond films. These findings can help to advance the development and optimization of devices and antiwear coatings based on diamond. [Display omitted] [ABSTRACT FROM AUTHOR]

It is highly desirable for electromagnetic wave (EMW) absorbers to have a low high filler ratio in matrix and low matching thickness. Herein, atomically dispersed Mn sites are introduced into N-doped carbon nanotubes (Mn−N x /NCNT) to this aim. Structural characterizations indicate that the as-fabricated Mn−N x /NCNT exhibits tubular morphology with a large surface area of 295.56 m2 g−1 and the Mn sites are atomically dispersed in the NCNT with a loading of 1.56 wt%. Benefiting from the unique structural advantages, Mn−N x /NCNT has excellent EMW absorption property, showing an effective absorption bandwidth of 4.15 GHz at a filler ratio of only 7% and a matching thickness of only 1.7 mm. The experimental measurements of electromagnetic parameters and density functional theory calculation results indicate that electronic structure and polarizability of the NCNTs are adjusted by the atomically dispersed Mn sites, leading to the increase in conduction and polarization losses of Mn−N x /NCNT, and thus in the EMW property. Our results demonstrate that hollow nanotubes containing metal single-atoms are potential EMW absorbers with a lightweight feature. [Display omitted] [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOF) derived carbon nanomaterials are arising as promising anode materials for sodium-ion batteries. However, the heteroatoms loss and aggregation during pyrolysis significantly hamper its further application. Herein, we utilized electrospinning structuring energetic MOF into nanofibers, followed by one-step sulfurization. The high content N doping (24.58 wt%) and CoS nanoparticles encapsulated carbon nanofibers with ultra-large interlayer distance (0.422 nm) were synthesized, which improved the diffusion properties and phase behavior of sodium ions. The resulting CoS/NSCNF (NSCNF for nitrogen and sulfur co-doped carbon nanofibers) delivered a superior rate performance of 358.5 mAh g−1 after 2250 cycles at 6 A g−1, serving as an anode for sodium-ion battery. The excellent storage performance ascribed to abundant N/S defects, enlarged carbon spacing, and the continuous one-dimensional structure of CoS/NSCNF, enhancing sodium ions storage ability contrasted with MOF-derived carbon. The density functional theory calculations further demonstrate that nitrogen-doping favors sodium ion adsorption ability of CoS/NSCNF, thereby improving storage performance. The high content N doping (24.58 wt%) and CoS nanoparticles embedded carbon nanofibers with ultra-large interlayer distance (0.422 nm) were synthesized by electrospinning and a one-step sulfurization process. The resulting CoS/NSCNF are presented as anode materials of SIB, delivered long-term cycling stability and superior rate performance of 358.5 mAh g−1 after 2250 cycles at 6 A g−1. [Display omitted] [ABSTRACT FROM AUTHOR]

The strong interaction between graphene and elemental ferromagnetic transition metals results in considerable shifts of the graphene π band away from the Fermi level. At the same time, a weakly-dispersing single-spin conical band feature is found in the proximity of the Fermi level at the K ̄ point in the surface Brillouin zone of epitaxially-aligned graphene/Co(0001). Here, the robustness of this electronic state against twisting angles at the interface is experimentally and theoretically demonstrated by showing the presence of similar band features also in the case of rotated graphene domains on Co(0001). Spin-resolved reciprocal space maps show that the band feature in rotated graphene has similar Fermi velocity and spin polarization as its counterpart in epitaxially-aligned graphene. Density functional theory simulations carried out for the experimentally observed graphene orientations, reproduce the highly spin-polarized conical band feature at the graphene K ̄ point, characterized by a hybrid π -d orbital character. The presence of the conical features in the rotated domains is attributed to the unfolding of the superstructure K ̄ point states exclusively to the K ̄ point of the graphene primitive cell. The similarities found in the electronic character for different graphene orientations are crucial in understanding the magnetic properties of realistic graphene/Co interfaces, facilitating their implementation in spintronics applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Acoustic plasmons in graphene exhibit strong confinement induced by a proximate metal surface and hybridize with phonons of transition metal dichalcogenides (TMDs) when these materials are combined in a van der Waals heterostructure, thus forming screened graphene plasmon–phonon polaritons (SGPPPs), a type of acoustic mode. While SGPPPs are shown to be very sensitive to the dielectric properties of the environment, enhancing the SGPPPs coupling strength in realistic heterostructures is still challenging. Here we employ the quantum electrostatic heterostructure model, which builds upon the density functional theory calculations for monolayers, to show that the use of a metal as a substrate for graphene-TMD heterostructures (i) vigorously enhances the coupling strength between acoustic plasmons and the TMD phonons, and (ii) markedly improves the sensitivity of the plasmon wavelength on the structural details of the host platform in real space, thus allowing one to use the effect of environmental screening on acoustic plasmons to probe the structure and composition of a van der Waals heterostructure down to the monolayer resolution. [Display omitted] [ABSTRACT FROM AUTHOR]

A well-defined methodology for constructing appropriate atomistic representations of biochar will aid in visualizing the structural features and elucidating biochar behavior with molecular dynamics (MD) simulations. Such knowledge will facilitate engineering biochars tailored to specific applications. To achieve this goal, we adapted modeling strategies applied in coal science by employing multi-cross-polarization 13C nuclear magnetic resonance, ultimate analysis, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy to identify functional groups. Helium density, surface area, and porosity were used to assess structural features. Biochar's aromatic cluster size distribution was proposed based on data from the benzene polycarboxylic acid method. The computational framework reduces bias by incorporating chemical information derived from density functional theory, reactive MD simulations, and advanced characterization data. The construction approach was successfully applied to cellulose biochars produced at four temperatures, obtaining independent representations with a relative error on the atomic contents of <10 % for oxygen and nitrogen and <5 % for carbon and hydrogen. The atomistic representations were validated using X-ray diffraction, electron spin resonance data, and laser desorption/ionization Fourier-transform ion cyclotron resonance-mass spectrometry. The code will assist others in overcoming structural creation barriers and enable the utilization of the generated structures for further simulations. [Display omitted] • Available code for creating large-scale atomistic models, capturing chemical and physical features. • A novel approach proposes the aromatic cluster size distribution of biochar. • Atomistic representations are validated with experimental and theoretical data. • The arrangement of aromatic size distributions aids in surface area and pore development. [ABSTRACT FROM AUTHOR]

Exploring the chemistry of materials at high pressure leads to discoveries of previously unknown compounds and phenomena. Here chemical reactions between elemental dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures up to 95 GPa and temperatures of ∼2800 K. In situ single-crystal synchrotron X-ray diffraction (SCXRD) analysis of the reaction products revealed the formation of novel dysprosium carbides, γ-DyC 2 , Dy 5 C 9 , and γ-Dy 4 C 5 , along with previously reported Dy 3 C 2 and Dy 4 C 3. The crystal structures of γ-DyC 2 and Dy 5 C 9 feature infinite flat carbon polyacene-like ribbons and cis -polyacetylene-type chains, respectively. In the structure of γ-Dy 4 C 5 , carbon atoms form dimers and non-linear trimers. Dy 3 C 2 contains ethanide-type carbon dumbbells, and Dy 4 C 3 is methanide featuring single carbon atoms. Density functional theory calculations reproduce well the crystal structures of high-pressure dysprosium carbides and reveal conjugated π -electron systems in novel infinite carbon polyanions. This work demonstrates that complex carbon homoatomic species previously unknown in organic chemistry can be synthesized at high pressures by direct reactions of carbon with metals. [Display omitted] [ABSTRACT FROM AUTHOR]

The quest for the materials that boast efficient electromagnetic interference (EMI) shielding, strong strength and superb thermal dimensional stability is a burgeoning research area, particularly due to their critical applications in safeguarding sensitive circuits against microwave radiation, especially in the space environments. Graphene-based composites, leveraging the remarkable attributes of individual graphene nanosheets, emerge as prime contenders for fulfilling these sophisticated application requirements. In this study, we prepared boron-graphene composites via spark sintering, combining graphene sheets and boron nanoparticles. This method not only ensures high-performance outcomes but also remains cost-effective and suitable for large-scale production. Boron serves as a binder, facilitating the connection between adjacent graphene sheets and enhancing the graphitization process. The resulting composites demonstrated exceptional electrical conductivity (4.53 × 105 S m−1) and superior EMI shielding effectiveness (average SE T 83 dB, with the thickness of 0.25 mm), markedly surpassing previous graphene-based materials in terms of compressive strength (171.3 MPa), and exhibiting low thermal expansion and an ultra-low friction coefficient (0.04). Additionally, to unravel the evolution of boron in the graphene composite and the impact of boron on electrical conductivity, first principles calculations and density functional theory (DFT) were utilized. This investigation underscores the significant promise of boron-graphene composites as high-performance, multifunctional materials across various domains. [Display omitted] • Boron-graphene composite was high-efficiently fabricated by SPS. • Boron plays a role as binders and promotes the graphitization of graphene. • The resultant composite demonstrates excellent EMI shielding effectiveness. • The resultant composite also shows outstanding multifunctional properties. • Density functional theory elucidates the evolution mechanism of boron in graphene. [ABSTRACT FROM AUTHOR]

The search for new two-dimensional (2D) carbon nitride (CN) materials with desirable properties is an important and critical area of research. This study presents a series of 2D CN materials with appealing features such as semimetal or flat bands. By utilizing group theory and graph theory, we perform a random search of the configurational space of 2D CN monolayers, leading to the identification of 721 new CN materials. Extensive density functional theory calculations were then conducted to evaluate their properties. We found that 57 materials exhibit semimetal behavior, while 664 display characteristics of semiconductors and normal metals. Notably, materials such as 51-5-16-C 3 N-r568 and 55-5-20-C 4 N-r568 feature topological Dirac semimetals with protected 1D topological boundary states. Moreover, 31 materials possess flat bands near their Fermi level, including two with kagome-like flat bands that induce intrinsic spontaneous magnetization due to partially-occupied flat bands. Our results offer several promising candidates for exploring physical phenomena related to semimetals or flat bands in 2D CN materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Metal clusters supported on carbonaceous substrates are of interest in catalysis, hydrogen storage, and other fields. In this paper, the structures and the infrared spectra of C 60 Rh n + (n = 1–6) fullerene-metal complexes are studied by a combination of mass-selective infrared spectroscopy and theoretical calculations. It is found that clustering of Rh on the surface of the fullerene is preferred over surface wetting. For Rh 4 + and Rh 6 +, the structures of the adsorbed clusters are different from those of the free clusters. There is electron transfer from the metal cluster to the fullerene in neutral C 60 Rh n , and in cationic C 60 Rh n + the electron deficit is shared by the metal cluster and the fullerene. Adsorption of Rh n clusters leads to degeneracy lifting of the most intense C 60 features in the infrared spectra that were measured in the 300–850 cm−1 range. Agreement is obtained, in general, between the experimental infrared spectra of D 2 -tagged C 60 Rh n + and the calculated spectra for untagged C 60 Rh n +, except in the 600–750 cm−1 region, where features mainly arise from the presence of D 2 -messenger molecules adsorbed on the Rh n clusters. [Display omitted] • A combined experimental and theoretical study on the interaction of Rh clusters with C 60 is performed. • Far-IR multiple photon dissociation spectroscopy of C 60 Rh n + tagged with D 2 reveals the vibrational spectra. • In parallel, vibrational spectra are calculated using Density Functional Theory. • The comparison delivers novel information on the structure of C 60 Rh n complexes. • Clustering of Rh on the surface of the fullerene is preferred over surface wetting. [ABSTRACT FROM AUTHOR]

Antimony-based materials represent promising anode materials for sodium ion batteries (SIBs) owing to their high theoretical capacity, however, the large volume expansion and low ionic conductivity during the electrochemical process prohibit them from reaching their theoretical expectations. In this work, Sb 2 S 3 @C and Sb 2 Se 3 @C nanodots with uniform diameters of 19.0 nm and 20.7 nm were synthesized by H 2 /C thermal reduction and co-sulfurization (selenization) of sodium stibogluconate. Each Sb 2 S 3 and Sb 2 Se 3 nanodot was coated by an interconnecting carbon network with weak graphitization, which further crosslinked together to form a high conductive framework. When applied as anode for SIBs, they exhibited desired sodium storage properties, especially the excellent cycling stability of Sb 2 Se 3 @C nanodots with a reversible capacity of 316.1 mA h g−1 after 100 cycles at 100 mA g−1 and 269.1 mA h g−1 after 200 cycles at 1 A g−1, which was consistent with the calculated result of theoretical volume changes (264% and 246%) and density functional theory (DFT) calculation for both materials during the Na+ intercalation processes, as expected. [Display omitted] • Sb 2 S 3 (Sb 2 S 3) nanodots/C composites have been successfully fabricated. • The volume changes of two materials during the Na+ insertion/deintercalation process have been calculated and analyzed in details. • The satisfactory sodium storage properties are achieved, which is consistent with the result of theoretical calculation. [ABSTRACT FROM AUTHOR]

A sample of highly orientated pyrolytic graphite (HOPG) was implanted with Cs+ ions in order to study the effect on the graphite matrix and the chemical form of Cs once embedded. The mean implantation depth was calculated to be ∼22 nm, allowing for investigation with X-ray Photoelectron Spectroscopy, (XPS), where both a traditional Al Kα X-ray source and a higher energy Ag Lα source was used for an increased sampling depth deeper into the surface. Analysis found that there was a reduction of sp 2 C–C bonding with increasing implantation dose, resulting in a total loss of sp 2 character at ∼6 atomic % Cs+. A striking increase in higher binding energy components (285.8–289.4 eV) in the C 1s spectra cannot be attributed solely to the presence of C–O species, instead indicating a dramatic re-ordering of the graphitic lattice to accommodate and neutralize the embedded Cs. XPS analysis indicates the formation of cesium carbonate within the graphitic material; this is reinforced by analysis of a Cs 2 CO 3 reference sample. Additionally, thermodynamics equilibrium simulations, supported by simplified density functional theory (DFT) calculations, are performed, leading to strong agreement with the XPS findings; that is, the most stable form of Cs within the graphite matrix is expected to be cesium carbonate (Cs 2 CO 3), which is in thermodynamic equilibrium with degraphitised HOPG and oxygenated degraphitised HOPG. [Display omitted] [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is a key reaction in metal-air batteries and fuel cells. Herein, a novel carbon-doped Co nanoparticle coated with a carbon layer supported on the ordered macroporous titanium oxide (C-doped Co@C@TiO 2) is designed as the highly efficient and stable ORR catalysts. The C-doped Co@C@TiO 2 achieves the superior catalytic activity with an onset potential of 0.867 V and a limiting current density of −6.59 mA cm−2, which is much lower than the commercial Pt/C (−5.93 mA cm−2). The turnover frequency (TOF) of the C-doped Co@C@TiO 2 at the potential of 0.3 V (0.091 s−1) is nearly four times than the commercial Pt/C (0.025 s−1). This outstanding catalytical performance is attributed to the unique C-doped Co layer in Co nanoparticles, which can stable the OOH* and promote the desorption of OH*, and accelerate the catalyst surface regeneration in ORR. Meanwhile, the outer C layer with mesoporous channels can improve the stability and poisoning resistant of the C-doped Co nanoparticles, and the C-doped Co@C@TiO 2 still retains 98% of the current density after the reaction for 60 h. It is worth noting that the assembled zinc-air battery with C-doped Co@C@TiO 2 as the air cathode exhibits an ultra-high open circuit voltage of 1.51 V and an excellent durability of more than 41.6 days. This work provides one of the most promising non-noble metal-based catalysts for efficient and stable oxygen reduction reaction. [Display omitted] • The C-doped Co@C@TiO 2 achieves the superior catalytic activity with an onset potential of 0.867 V and a limiting current density of −6.59 mA cm−2. • The unique C-doped Co layer in Co nanoparticles can stable the OOH* and promote the desorption of OH*, and accelerate the catalyst surface regeneration in ORR. • The outer C layer with mesoporous channels can improve the stability and poisoning resistant of the C-doped Co nanoparticles. • The C-doped Co@C@TiO 2 has a current density retention rate of more than 98% after 60 h current-time test, which is significantly better than commercial Pt/C (66%). • The znic-air battery with C-doped Co@C@TiO 2 as the air cathode has a cycle stability of 41.6 days. [ABSTRACT FROM AUTHOR]

Surface modification of diamond with the addition of (sub)monolayer of metals or other electropositive adsorbates than the bulk carbon can result in negative electron affinity (NEA). Surface coverages of up to one-monolayer (<1 ML) of scandium on clean, oxygenated and nitrogenated diamond (100) surfaces were studied via plane-wave density functional theory (DFT) calculations. Adsorption of Sc on diamond is energetically favourable; for example, 0.25 ML coverage of Sc on the oxygenated diamond (100) surface has an extremely large calculated adsorption energy per adsorbate atom of −8.68 eV. Moreover, the majority of stable Sc-adsorption configurations possess NEA, with the most negative values of −3.73 eV, – 3.02 eV and −1.75 eV being found for 0.25 ML Sc coverage on the oxygenated, bare and nitrogenated diamond surfaces, respectively. These results predict that Sc termination on diamond should provide a thermally stable surface with large NEA, and is therefore a highly promising candidate for thermionic and other electron-emission applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we report high-pressure Raman experiments (0 − 28 GPa) in two different systems, i.e. , linear carbon chains encapsulated by multi-walled (C n @MWCNTs) and double-walled (C n @DWCNTs) carbon nanotubes. By running high-pressure cycles, it is observed basically two changes in the Raman spectra of chains that are the softening and disappearance of C n modes. We attributed the irreversible redshift of the C n band to the coalescence between adjacent chains. On the other hand, the disappearance of the C n band at the onset of the CNT collapse pressure is assigned to the tube-chain cross-linking. This effect appears to be independent of the C n length and the number of walls of the tubes, depending only on the innermost CNT diameter. We show that the pressure to coalesce longer chains is higher than 10 GPa. Density functional theory and molecular dynamics calculations were performed in order to support the interpretation of experimental data. The calculations show an irreversible pressure-induced softening of frequency of the confined linear carbon chain. Furthermore, molecular dynamics calculations showed that coalescence between the shorter chains occurs in a region of lower pressure than that of the longer chains, thus supporting the experimental observations. Our findings shed new light on the understanding of the C n @CNT system stability and pave the way for using high-pressure to obtain ultra-long chains (at lower pressures) and ultra-hard composites (at higher pressures). [Display omitted] [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO 2) is one of the promising anode materials for sodium-ion batteries (SIBs) owing to its high theoretical capacity (335 mA h g−1), reasonable operation voltage (0.7 V), low cost, and low toxicity, but suffers from its low electronic conductivity and ionic diffusion coefficient. Here, the novel mesoporous hollow TiO 2-x /C nanofibers were designed and synthesized by the simple coaxial electrospinning with the annealing treatment in H 2 /Ar atmosphere (H–TiO 2-x /C). Benefitting from the oxygen vacancies (OVs), mesoporous hollow nanofibers, and conductive carbon framework, the electronic conductivity and ionic diffusion coefficient of H–TiO 2-x /C are remarkably enhanced. The as-synthesized H–TiO 2-x /C demonstrates an excellent reversible capacity of 262.4 mA h g−1 at 33.5 mA g−1, superior rate performance of 142.6 mA h g−1 at 1.675 A g−1, and prominent capacity retention of almost 100% with a capacity of 131.3 mA h g−1 over 7000 cycles under a current density of 3.35 A g−1. Moreover, the in-situ X-ray diffraction analysis and density functional theory calculation reveal that the H–TiO 2-x /C possesses stable structure and low energy barriers. Furthermore, Na-ion full-cell of Na 0.67 Ni 0.33 Mn 0.37 Ti 0.3 O 2 //H–TiO 2-x /C delivers an energy density of 398.2 Wh kg−1 with a retention of 95.1% after 100 cycles at 0.335 A g−1. This work indicates the great promise of the novel mesoporous hollow H–TiO 2-x /C nanofibers as high-performance anode materials for SIBs. [Display omitted] • The mesoporous hollow H–TiO 2-x /C nanofibers with multi-function are synthesized. • H–TiO 2-x /C delivers ultrahigh cyclic stability at a current density of 3.35 A g−1. • The structural evolution and storage mechanism is investigated for H–TiO 2-x /C. [ABSTRACT FROM AUTHOR]

Investigations of clathrate structures have gained a new impetus with the recent discovery of room-temperature superconductivity in metal hydrides. Here we report the finding, through density functional theory calculations, of a clathrate phase in the fullerite C 60 system. Intermolecular bonds of the type 5/5 2+3 cycloaddition are induced between each C 60 molecule and its twelve nearest neighbors in the face centered cubic lattice. Remarkably, this bonding creates on octahedral sites new C 60 cages, identical to the original ones, and on tetrahedral sites distorted sodalite-like cages. The resulting carbon clathrate has a Pm 3 ¯ simple cubic structure with half of the original face centered lattice constant. Eighty percent of its atoms are sp3-hybridized, driving a narrow-gap semiconducting behavior, a moderate bulk modulus of 268 GPa and an estimated hardness of 21.6 GPa. This new phase is likely to be prepared by subjecting C 60 to high pressure and high temperature conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon nitride nanoporous lattices are nowadays among the most appealing two-dimensional (2D) nanomaterials for diverse cutting-edge technologies. In one of the recent advances, novel C–C bridged heptazine of C 6 N 7 with a nanoporous structure has been fabricated. Based on the experimentally realized C 6 N 7 lattice and by altering the linkage chemistry, we introduce three novel carbon nitride lattices of C 6 N 7 –C 2 , C 6 N 7 -BN and C 6 N 7 –C 2 H 2. Density functional theory (DFT) simulations are next utilized in order to investigate energetic stability, electronic, mechanical response, and optical characteristics of novel C 6 N 7 -based monolayers. The dynamical stability and mechanical properties are explored using machine-learning interatomic potentials (MLIPs). The presented results confirm that C 6 N 7 -based monolayers are stable and strong semiconductors with notable absorption of the ultraviolet range of light. Remarkable accuracy of the developed computationally-efficient classical models is confirmed by comparing the predictions with those by DFT. Findings by the combined DFT and MLIP methods confirm the stability of novel C 6 N 7 -based nanosheets and provide a comprehensive vision on their highly appealing physical properties. More importantly, this study confirms the outstanding robustness and efficiency of MLIPs in substituting the computationally expensive DFT methods in the exploration of complex phononic and mechanical/failure responses of low-symmetry and highly-porous conductive frameworks. [Display omitted] [ABSTRACT FROM AUTHOR]

The past two decades witnessed the thriving of non-conventional nanoparticles in catalytic synthesis of single-walled carbon nanotubes (SWNTs). However, most of the SWNTs are limited to growing on a flat surface which usually suffers low output, thus making the evaluation of SWNT chirality distribution challenging. In this work, we report a solid magnesia (MgO) supported ruthenium (Ru) catalyst for chemical vapor deposition (CVD) growth of SWNTs with sufficient quantity for optical characterizations. Both MgO supported atomically dispersed Ru catalyst and Ru nanoparticles pre-deposited onto porous MgO are active for catalytic synthesis of small diameter SWNTs. Particularly, enriched (6, 5) SWNTs are achieved at temperatures higher than 800 °C by CO CVD, which is partially attributed to the high activity of Ru clusters. Besides, density functional theory (DFT) calculations reveal that the charge transfer from the MgO support to the Ru clusters promotes the carbon precursor absorption and dissociation, accounting for the activation of Ru clusters. This work not only demonstrates the application of atomically dispersed catalyst for CVD growth of SWNTs, but also paves the way for the chirality-selective growth of SWNTs from non-magnetic nanoparticles. Atomically dispersed Ru catalyst supported by porous MgO is designed for growing single-walled carbon nanotubes by CO chemical vapor deposition. Owing to the charge transfer from MgO to Ru clusters, which are formed from atom aggregation during reaction process, the supported metal Ru catalyst is shifted into "Goldilocks zone" for preferential synthesis of (6, 5) tubes. [Display omitted] [ABSTRACT FROM AUTHOR]

Au nanoparticles with diameters about 1.4 nm were dispersed onto porous Si 3 N 4 grids and applied for growing single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition. Particularly, SWCNTs with diameters in the range of 0.75–1.8 nm were produced at a reaction temperature of 700 °C using CO as the carbon precursor. Nanobeam electron diffraction characterizations revealed that most of the SWCNTs have large chiral angles and zigzag SWCNTs were hardly detected. Density functional theory calculations showed that the SWCNT-Au interface formation energy and the SWCNT growth kinetics account for the enrichment of large chiral angle SWCNTs in the product. To correlate single-walled carbon nanotube chirality with the element of Au, thermal chemical vapor deposition growth is performed on uniform Au nanoparticles at 700 °C using CO as the carbon precursor. The nanotube chirality distribution is determined by electron diffraction technique, which reveals a bias to large chrial angle species, a result of low tube-Au interface formation energy and high stability of the extruded edge hexagons. [Display omitted] [ABSTRACT FROM AUTHOR]

A diamond-based material C 63-x Si x V compound is engineered by using density functional theory calculations. In the C 63-x Si x V compound, (1 + x) C atoms in the 2 × 2 × 2 diamond supercell are replaced by x Si and one V atoms. In this way, a bandgap-regulable intermediate-band (IB) photovoltaic material would be gotten. The calculational results indicate that it can reduce the bandgap of the diamond without changing the character of its band structure to substitute Si atoms for several C atoms in the diamond. And the bandgap decreases along with the increase of Si content. When the atomic concentration of Si is lower than 6.25%, the implantation of Si has less effect on the width and electron filling of the IB for the C 63-x Si x V compound. With the increase of Si content, the IB in the bandgap shifts toward the VB and the sub-bandgap absorption of the C 63-x Si x V compound shifts to longer wavelength range. Results of partial density of states indicate that the IB formed by implanting V in the diamond is mainly composed of the d states of V, while the contribution of the Si is negligible. [Display omitted] [ABSTRACT FROM AUTHOR]

From as small as single carbon dimers up to giant fullerenes or amorphous nanometer-sized particles, the large family of carbon nanoclusters holds a complex structural variability that increases with cluster size. Capturing this variability and predicting stable allotropes remains a challenging modelling task, crucial to advance technological applications of these materials. While small cluster sizes are traditionally investigated with first-principles methods, a comprehensive study spanning larger sizes calls for a computationally efficient alternative. Here, we combine the stochastic ab initio random structure search algorithm (AIRSS) with geometry optimisations based on interatomic potentials to systematically predict the structure of carbon clusters spanning a wide range of sizes. We first test the transferability and predictive capability of seven widely used carbon potentials, including classical and machine-learning potentials. Results are compared against an analogous cluster dataset generated via AIRSS combined with density functional theory optimizations. The best performing potential, GAP-20, is then employed to predict larger clusters in the nanometer scale, overcoming the computational limits of first-principles approaches. Our complete cluster dataset describes the evolution of topological properties with cluster size, capturing the complex variability of the carbon cluster family. As such, the dataset includes ordered and disordered structures, reproducing well-known clusters, like fullerenes, and predicting novel isomers. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we used Cl/S co-doped carbon nitride nanotube clusters (Cl/S-TCN) photocatalyst to effectively drive the metal-free photo-Fenton (MF-PF) reaction. The synergistic effect of Cl/S-TCN and H 2 O 2 made MF-PF (Cl/S-TCN) system have excellent degradation performance for organic wastewater in a wide pH range (3–9). The optimal amount of H 2 O 2 was only 10 mM, the degradation rate of p-nitrophenol (p-NP) by MF-PF (Cl/S-TCN) system under neutral conditions can be increased from 50.3% to 98.2%, the degradation rate of tetracycline (TC) reached more than 90% within 20 min, and the COD removal rates of domestic sewage and oilfield produced water reached 70.3% and 82.6% accordingly. MF-PF (Cl/S-TCN) system had excellent stability, and the performance loss was less than 0.7% after four cycles of experiments. Density functional theory calculations showed that Cl and S dopants accelerated the separation of photogenerated electrons and holes on the surface of Cl/S-TCN. These photogenerated electrons and holes, were used as electron donors and electron acceptors for reacting with H 2 O 2 , destroyed the O–O bond and O–H bond of H 2 O 2 , and finally converted H 2 O 2 to •OH and •O 2 − with strong oxidation, which is the key to enhance the performance of MF-PF (Cl/S-TCN) system. Such reaction pathway was rarely reported in previous studies. [Display omitted] • Prepared Cl/S-TCN photocatalyst with strong visible light response. • Cl/S-TCN effectively drives the metal-free photo-Fenton reaction under visible light. • Photogenerated e− and h+ can quickly convert H 2 O 2 to ROS. • Cl and S dopants promote the separation of e−- h+ pairs on the surface of Cl/S-TCN. [ABSTRACT FROM AUTHOR]

Graphene is one of the most intriguing two-dimensional carbon materials. Its mechanical strength and failure are key concerns for materials engineering and applications. Despite the success of fracture mechanics, the mechanism of how pristine materials fail remains an elusive problem. While many theoretical studies based on molecular dynamics using empirical forcefields have tried to address this question, atomic-scale mechanics are not clearly understood. Especially, a widely employed bond-breaking approach based on the critical bond length has not been rigorously tested. Here, utilizing molecular dynamics simulations with density functional based tight binding, we investigate how the failure of the pristine material initiates. The Wiberg bond order (W BO) to estimate the change of chemical bonds shows a transition from sp2 (W BO ∼ 1.33) to sp3 (W BO < 1.0) during the deformation. However, it reveals that a single threshold value for either the W BO or bond length is insufficient to decide failure of pristine material without free edges or defects. Instead, collective behaviors of the local atomic group govern the fracture initiation of pristine graphene. Our study provides dynamic mechanical responses based on quantum mechanics, which have not been captured by empirical forcefields, opening opportunities to design properties by precisely coupling the mechanics and quantum mechanics. [Display omitted] [ABSTRACT FROM AUTHOR]

Since Earth-abundant materials have received considerable attention for energy applications, interest in developing new carbon-based structures actively continues. One such material, the 3D carbon-based schwarzite structure, has the unusual shape of Triply-Periodic Minimal Surfaces (TPMS) and shows a stable curvature formed of carbon rings with more than six atoms. However, the possibility of application as a catalytic material has not been discussed, even though their geometric and electronic features can improve reactivity with diverse catalytic adsorbents. Herein, we systematically investigated the hydrogen evolution reaction (HER) activity of diverse schwarzites based on thermodynamic, electronic, and geometric viewpoints. Our results reveal that the h8326896 structure has superior HER catalytic activity with binding free energy of hydrogen (Δ G H ∗ ) as −0.02 eV, closer to that of the ideal catalyst (0 eV). Based on this thermodynamic result, we explored the reason for the remarkable activity and found that efficient hydrogen binding clearly originates from the favourable p -orbital tendency with a metallic nature and positively curved geometry. Therefore, we believe that this work will play an important role in uncovering and extending the utility of carbon-based schwarzites as catalytic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbyne, i.e. an infinitely long linear carbon chain (LCC), has been at the focus of a lot of research for quite a while, yet its optical, electronic, and vibrational properties have only recently started to become accessible experimentally thanks to its synthesis inside carbon nanotubes (CNTs). While the role of the host CNT in determining the optical gap of the LCCs has been studied previously, little is known about the excited states of such ultralong LCCs. In this work, we employ the selectivity of wavelength-dependent resonant Raman spectroscopy to investigate the excited states of ultralong LCCs encapsulated inside double-walled CNTs. In addition to the optical gap, the Raman resonance profile shows three additional resonances. Corroborated with DFT calculations on LCCs with up to 100 carbon atoms, we assign these resonances to a vibronic series of a different electronic state. Indeed, the calculations predict the existence of two optically allowed electronic states separated by an energy of 0.14–0.22 eV in the limit of an infinite chain, in agreement with the experimental results. Furthermore, among these two states, the one with highest energy is also characterized by the largest electron-vibration couplings, which explains the corresponding vibronic series of overtones. [Display omitted] [ABSTRACT FROM AUTHOR]